Liquid extractionis an operation used to separate the components of a liquid mixture of two or morespecies. In the simplest case, the mixture containstwo components: a solute (A) and a liquid solvent(B). The mixture is contacted in an agitated vessel with a second liquid solvent (C) that has two keyproperties: A dissolves in it, and B is immiscible or nearly immiscible with it. (For example, B maybe water, C a hydrocarbon oil, and A a species soluble in both water and oil.) Some of the A transfersfrom B to C, and then the B-rich phase (the raffinate) and the C-rich phase (the extract) separate fromeach other in a settling tank. If the raffinate is then contacted with fresh C in another stage, more Awill be transferred from it. This process can be repeated until essentially all of the A has beenextracted from the B